Self-referencing interferometers find use in laser beam analysis, in various optical testing procedures, and as wavefront sensors for aligning and controlling adaptive optical systems. The function of a self-referencing interferometer is to measure the phase distribution of an optical wavefront directly without need for a reference wavefront. Self-referencing interferometers used as wavefront sensors are generally required to be highly accurate, light-efficient and stable over relatively long periods of time. Furthermore, self-referencing interferometers are required to be capable of making wavefront phase distribution measurements at high speed. The types of self-referencing interferometers most commonly used in the prior art were point-diffraction interferometers and shearing interferometers.
Point-diffraction interferometers are characterized by low light efficiency, and by sensitivity to focussing and tilt errors. These are significant disadvantages in applications in which the wavefront source is apt to be dim, or in applications in which thermal gradients or mechanical forces are apt to cause structural deformations of the interferometer.
Shearing interferometers generally require complicated optical systems and electronics to obtain wavefront phase measurements along two orthogonal axes simultaneously, and to perform two-dimensional integration for phase reconstruction.